Hitherto, in aqueous solution systems, it is known to use a method of forming a coated film which comprises simultaneously applying silver halide emulsions containing gelatin as a binder using a slide hopper coating apparatus or an extrusion hopper coating apparatus, etc., to form a multilayer film, gelatinizing the multilayer film utilizing the gel-sol conversion characteristics of gelatin by cooling or using cold air to produce a superhigh viscosity state where the viscosity is in the tens of thousands to hundreds of thousands cps range. This makes it difficult for mixing between layers to occur. Subsequently, hot air, etc., is used for drying.
On the other hand, in organic solvent systems, when multilayer application and drying are merely carried out, diffusion and mixing easily occur not only in the drying zone but also in the bead forming area of the applied multilayer during application and drying, because of the low surface tension as compared with that of an aqueous solution system. Further, diffusion and mixing occur during drying because there is no sol-gel conversion process. As a result, it is very difficult to obtain a coated film where each layer is in a separated state.
Further, in the organic solvent systems, no good sol-gel conversion substance can be used in various kinds of solvents and no other effective method is available. Therefore, multilayer application or coating using organic solvent systems has been carried out by methods comprising applying or coating layers one after another and drying successively.
Successive application drying processes include a method which comprises rolling up the coated material after each application and drying or a method which comprises continuously applying and drying using a plurality of application drying devices. However, the former method involves a long production time and, consequently, a large production cost arises. In the latter method, very expensive equipment for production must be used because an application device and the drying device corresponding to each layer are required. Consequently, the production cost is high.
Recently, several methods of forming a coated film in which a hardening phenomenon of the coated film by irradiation of electron beams is utilized have been proposed. Japanese Patent Publication No. 19894/79 and Japanese Patent Application (OPI) No. 38160/81 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") disclose the above-described methods of forming a monolayer coated film, and Japanese Patent Publication No. 16403/78 and Japanese Patent Application (OPI) No. 24384/83 disclose the above-described methods of forming a multilayer coated film. However, they do not essentially solve the above-described problems, because active rays are irradiated successively after application of coated layers one by one in case of a multilayer coated film.